Yes, spark plug gaps affect performance. This abstract in a 2013 AVTECH Conference paper has noticed that gaps widen as a spark plug ages because the electrodes erode and oxidize. This increases the energy a coil must provide to generate the spark that ignites the air/fuel mixture. If the gap is too wide, the spark won’t cross the distance between the electrodes. As a result, the vehicle won’t start. If the vehicle starts, you can’t rule out misfires as a potential consequence.
A small gap makes this crossing easy, but the spark is less likely to ignite the mixture.
You must find a middle ground where the gap is wide enough to make ignition as efficient as possible but not so broad that the spark plug fails to perform its task. Manufacturers don’t concern themselves with the distinct needs of individual vehicles. Instead, they make plugs with gaps that fit the majority of engines.
And for the most part, those pre-gapped spark plugs work without additional adjustments. This proves gaps are important but not crucial. This paper from Tawfik Badawy, Hongming Xu, and XiuChao Bao in Applied Energy (Volume 191) appears to disagree because it argues that a wider spark plug gap reduces cyclic variations and makes the combustion process more stable, increasing the engine output in the process.
What Are The Consequences Of Having A Too-Wide Spark Plug Gap On Performance?
A spark plug with a broader gap uses more voltage to ignite the air/fuel mixture.
According to this NGK Spark Plugs, increasing the gap is a good thing because it elevates the spark’s exposure to the air-fuel mixture, maximizing efficiency.
But what if the gap gets too wide? The spark becomes weak, particularly when the voltage is insufficient to compensate for the distance. The weak spark will limit the amount of energy the car uses to ignite the mixture.
Keep an eye out for misfires, engine rattling, and cylinder drag, which occur because the spark has started skipping at higher speeds.
Your driving habits can affect the engine’s response to the gap. For instance, you can increase the gap by 0.010 inches if you drive the vehicle normally. This will give you the best performance and fuel economy.
But if you prefer to drive at full throttle, reducing the gap by 0.010 inches will do wonders for the engine’s performance. These considerations and any modifications you’ve made are important because spark plug gap requirements can differ drastically.
A gap that is too wide for one car might be acceptable for another engine. The engine’s reaction will tell you whether your adjustments are correct or wrong.
Can A Too-Narrow Spark Plug Gap Negatively Affect Vehicle Performance?
Yes, it can. Keep in mind that wide gaps are preferable because they allow long, robust sparks to form. They also maximize contact between the spark and the air/fuel mixture. A narrow gap does the opposite. It generates a weak, unreliable spark that promises partial ignition. Expect one or more of the following consequences:
- The engine may refuse or delay to start.
- The vehicle will accelerate slowly. The engine won’t respond as quickly when you step on the throttle.
- The engine will misfire because the spark plugs cannot ignite the air/fuel mixture.
- Rough idling.
- Engine knocking.
- The engine’s output will deteriorate.
- Poor gas mileage.
- The spark plugs will wear out quicker than you expect.
It is worth noting that the symptoms above can also manifest because of bad spark plugs. A wide or narrow gap is not the same as a bad spark plug. You can adjust a plug whose gap is too wide or narrow. But if the spark plug fails, you must replace it.
How can you differentiate between the two? The simplest solution is to measure the gap. You can also inspect the spark plug for the following:
- Soot
Soot on the insulator tip and electrodes appears because of clogged filters and a rich air/fuel mixture. Many mechanics use the term ‘Carbon Fouled’ to refer to spark plugs with soot.
- Oil
Oil can infiltrate the pistons and cylinders to form black deposits on the electrodes and insulator tip. It isn’t enough to clean the plug. You must identify the source of the leak.
- Water
Spark plugs can become wet because of flooding. This fault is not as severe as soot or oily deposits. In fact, you can wait for the spark plugs to dry out. You don’t have to clean them.
- Burns
The electrodes can melt because of excess heat. Look for blistered insulator tips and white deposits.
- Physical Damage
The electrodes can wear out, flatten, and break. This can happen because you installed the wrong spark. Or maybe you added the correct spark plug using the wrong tools and methods.
The experts at NGK Spark Plugs have published pictures of spark plugs with different faults. Take a moment to determine whether your spark plug resembles one of those images before you blame the gap.
How Can Adjusting The Spark Plug Gap Enhance Engine Performance?
Anyone can adjust the spark plug gap if they have the right tools, although the practice is risky because spark plugs are brittle, and you can break them. You can’t proceed until you measure the gap.
This happens after you clean the plug. Otherwise, debris and deposits on the electrodes may skew your readings. Once you determine the gap measurements, you can compare them to the manual’s recommendation.
You should only adjust the gap if its measurements differ from the manual’s recommendation. In an ideal situation, increasing the gap will benefit the vehicle by increasing the engine’s output and reducing hydrocarbon emissions.
A wide gap maximizes efficiency during ignition and combustion. If the gap is too broad, narrowing it will eliminate misfiring, slow acceleration, and rough idling.
Are There Recommended Spark Plug Adjustments For Different Driving Conditions?
The average spark plug gap is 0.020 – 0.040. The exact measurements will vary with each brand.
The driving conditions don’t influence the spark plug gap. This is because they change frequently, and you can’t adjust the spark plug gap every time the driving conditions change. Try to identify a spark plug gap that fits your engine’s requirements. Let the engine worry about the driving conditions. If you have concerns about the gap, install the plugs and keep an eye out for the following:
- Does the engine sound smooth or rough when you run it?
- Do you hear knocking and pinging?
- Does the engine start easily? Does it struggle? Does it respond on the first try?
- Does the engine generate the power you expect? Does it accelerate whenever you step on the gas? Does it shake?
- Does the engine run on the same fixed volume of fuel, or have you noticed fluctuations? Are you satisfied with the fuel economy?
- Do the spark plugs wear out faster than usual?
The answers to these questions will determine whether you should increase or reduce the spark plug gap.
Can A Properly Set Spark Plug Gap Improve Both Power And Fuel Efficiency?
Yes, it will. The gap determines the strength and consistency of the spark jumping between the electrodes. This, in turn, affects the efficiency of ignition and combustion. Efficient ignition and combustion results in an increase in the engine’s power output and better fuel efficiency.
Modifications to the engine can skew the results. For instance, conventionally wide gaps may prove insufficient for engines with higher compression, high flow intake ports, and a high RPM.